Friction plate clutches have a provision for passing fluid such as oil between the clutch plates so as to lubricate or cool the plates. Furthermore other multi-plate clutches have attempted to prevent plate flutter and have been successful to some extent. Such devices are shown in U.S. Pat. No. 4,068,747 which issued Jan. 17, 1978 to Snoy and entitled "Multi-Plate Clutch Having Means to Prevent Clutch Flutter", wherein the outer periphery of the plates were formed as flat portions or spots which act as cams when the adjacent discs rotate relative thereto and thereby resist the tendency to flutter. U.S. Pat. No. 3,631,953 also issued to Snoy on Jan. 4, 1972 entitled "Friction Plate Clutch Having Means To Dampen Plate Flutter" utilized resilient means between the radially inner set of clutch plates and which purposely caused the plates to go into a mode of flutter so that the flutter could then be damped by split type outer clutch plates.
Yet another example of a prior art attempt to eliminate clutch flutter is shown in the Hilpert U.S. Pat. No. 3,472,348 issued Oct. 14, 1969 entitled "Clutch Having Radially Shiftable Means To Prevent Flutter", and wherein grooved weights were shifted radially outwardly so as to engage the inner periphery of the inner set of plates to thereby mechanically hold the plates in properly spaced relationship and resiliently prevent axial movement or flutter of the plates. These three above mentioned patents have been assigned to an assignee common with the present invention and while they did prove successful for their intended purposes in certain clutch uses, with the advent of very large clutches, the flutter problem continues to persist and has prohibited the use of friction plate clutches in extremely large installations, such as for example that are found in marine vessels.
Other types of multiple and interleaved friction plate clutches have attempted to control the coolant flow between the plates of a clutch, for the purpose of urging the clutch applying means to a clutch releasing direction or for maximizing the supply of cooling fluid to the plates upon engagement. However, the problem of clutch flutter does not occur when the clutch is engaged, but rather occurs when the clutch is in the release condition when the plates are separated from one another and the two sets of plates are counter-rotating.